Why have I developed a rash on my left leg several days after the beginning of back pain? When I went to the doctor and was asked about numbness and rash I didn t have them at that time. What can I do about it? I am 66, my height is 5ft 6in., my weight is 160. I have been having back pain from time to time, but it usually goes away with rest. This time is was severe and has been going on for a week. I have been taking a muscle relaxant , 800 mg. Ibuprofin and vicadin. I have been to a doctor twice.